Are there plug-in hybrid vehicles in America's future? Such hybrids could travel 10 to 20 additional miles on battery power alone, but until recently automakers have said -- more or less unanimously -- that it was not practical to add a larger battery pack and plug-in chargers to hybrid vehicles because of the added weight, complexity and cost.

The public is already confused about hybrids, they say, with many people still believing that these cars (whose batteries are charged by their internal-combustion engines) need to be plugged in. So now hybrids really will have a power cord?

Maybe, says DaimlerChrysler. The company recently showed in New York the first vehicle in its small test fleet of Dodge Sprinter delivery vans with plug-in-hybrid power trains. The Sprinters can drive 20 miles on batteries alone, powered by a 70-kilowatt electric motor. The three Sprinters currently in the United States (built in Germany with either diesel or gasoline engines) are the vanguard concept vehicles in a four-truck fleet; another three dozen will enter service around the world.

This does not necessarily mean that DaimlerChrysler will make plug-in production Sprinters for sale, but the company appears to be warming to the concept.

Other companies are mulling the idea, too.

Ford Motor's chairman, William Clay Ford Jr., said in May that his company was "keenly looking at" the technology. At Toyota, Dave Hermance, executive engineer for advanced technology vehicles, confirmed that the company has started a research and development program for plug-ins. "But we believe the batteries are not ready for production," he added.

According to a Bloomberg News report in June, General Motors is also developing a plug-in hybrid. Even Google.org, a charitable for-profit company set up by the popular search engine provider, said it would create its own plug-in system.

A June report by AllianceBernstein, an investment management firm in New York, titled "The Emergence of Hybrid Vehicles," concluded that "Plug-in hybrid vehicles are likely to arrive as an extension of current hybrid technology." The fuel-efficiency gains, the report said, "would be enormous for those people who typically drive only short distances each day."

Plug-ins, like all hybrids, excel in stop-and-go duty. And their ability to make those runs on batteries alone makes them ideal for the delivery tasks envisioned for the Sprinter project.

The Electric Power Research Institute, a trade association for utilities, estimates that a plug-in hybrid would consume 2,000 to 2,500 kilowatt-hours of grid electricity annually. So wouldn't vehicles like the plug-in hybrid Sprinter simply transfer their pollution source from the tailpipe to the smokestack of a coal-burning power plant?

That depends on the source of electric power, according to a report released last month by the American Council for an Energy-Efficient Economy, a nonprofit energy policy group. The council concluded that a plug-in version of the Toyota Prius could reduce carbon dioxide emissions by a third compared with today's Prius hybrid, but only if its batteries were charged with California electricity -- generated mainly from relatively clean sources.

"One of the key determinants is whether the electricity is generated using coal," Jim Kliesch, a co-author of the report, said in an interview. The report says that in a part of the Midwest dominated by coal-burning power plants, a plug-in Prius would generate 1 percent more carbon dioxide. "Our position is that overselling plug-ins to policymakers or to John Q. Public has the potential of causing disenchantment with the technology," Kliesch said.

But the plug-in concept has long been championed by environmentalists and green-minded entrepreneurs, some of whom have added battery packs and chargers to existing hybrids like the Prius and the Ford Escape. On short commuting runs, these cars wouldn't need to start their gasoline engines, allowing their champions to claim very high potential economy figures. But some homemade plug-in hybrids have had problems adapting to the software of the cars' sophisticated on-board computers.

"This DaimlerChrysler introduction is the beginning of the automakers fulfilling our dreams," said Felix Kramer, a founder of CalCars.org, which has championed plug-in hybrids and helped build prototypes. "It's very encouraging."

The van of dreams is a conventional-looking Sprinter, familiar to Americans as a tall Dodge or Freightliner utility vehicle used as a passenger bus and, without rear seats, as a delivery truck. In Europe, it is badged as a Mercedes-Benz. Departures from factory specifications include a plug-in recharging port on the right side of the van's nose, a small switch on the dashboard that shifts the vehicle into electric-only mode and a 350-pound, 14-kilowatt-hour lithium-ion battery pack peeking out from under the flat floor. And, of course, Hybrid Sprinter lettering on its flanks.

The Sprinter drew a crowd to the lobby of the Solaire apartment tower in Battery Park City, chosen because it is the first green high-rise residential building in the United States (with its own wastewater plant and photovoltaic panels).

The Sprinter project is a team effort involving DaimlerChrysler, the New York Power Authority and the Electric Power Research Institute, among others; representatives of each were on hand for the introduction. "The plug-in hybrid is a good application for fleets, and terrific for New York City," said Timothy Carey, president and chief executive of the power authority, who drives an Escape Hybrid.

The officials stood under an awning and looked on as I became the first journalist in the United States to drive the Sprinter.

I twisted the key, and was amazed at how quiet the truck was. Unfortunately, it wasn't running. To the consternation of almost everyone there, this would-be paragon of New York fleet use had failed to start.

A German engineer quickly connected a laptop computer to troubleshoot the failure, and concluded that the van's motor controller was not functioning. Unfortunately, he couldn't fix the problem quickly and the demonstration drive was postponed.

According to a DaimlerChrysler spokesman, Nick Cappa, the car was running half an hour later. But I didn't connect with it again until several days later, in White Plains, where the power authority has its headquarters. The facilities also include a charging station, which takes six to eight hours to replenish the Sprinter's lithium-ion batteries. The paddle charger fits into a slot in the front fender and is pushed downward to start the electricity flowing. The charging system is designed with safety in mind: the electrical contacts are not exposed until the paddle is inserted into the car.

John Markowitz, a power authority engineer with temporary custody of the hybrid Sprinter, explained that this van, with a gasoline engine, was destined for California, where regulators are not friendly to diesels.

That van's lithium-ion batteries offer the same amount of energy storage as the nickel-metal-hydride packs in the other version, but weigh half as much. But lithium-ion batteries pose some cost and durability challenges: Both Apple Computer and Dell have recalled lithium-ion laptop computer batteries because of an overheating hazard.

The Sprinter is relatively simple to drive, with an automatic transmission that offers manual shifting. It handles well for a large vehicle. The driver can choose either hybrid or electric-only mode, with the latter providing the strongest initial acceleration.

The 2.3-liter gasoline engine in my test vehicle revved to 5,000 rpm without providing much forward motion up hills, but the electric motor's abundance of low-speed torque pulled it away smoothly -- and with much less noise than a conventional van.

The engine engagement is not quite as seamless as it is on the production Prius or Escape, but as in those cars, the engine shuts off neatly at stoplights. The alternate version, with a 2.7-liter turbocharged diesel engine, is likely to move out quicker.

In the first phase of testing, Sprinters will be deployed in New York, Kansas City and Los Angeles. The Kansas City and Los Angeles vans will go into service at utility companies. The Sprinter to undergo a three-year test in New York will be a diesel version with nickel-metal-hydride batteries. It will be used by the New York Times to deliver newspapers from a printing plant in College Point, Queens, to routes in five boroughs, and to haul newspapers to schools, said Mark Coleman, director of distribution for the Times. He said the van was likely to be delivered in February or March.

The Sprinter will have company. Claus Tritt, senior manager for commercial vehicles, said DaimlerChrysler would also field a second plug-in hybrid on a revised platform, though he declined to comment further. "It will have wheels," he confided.